Improve unittests.
Rename loop variables.
Change some function parameter from const to in.
[Cleanup] Some cleanup.

* Change function parameters from const -> in.
* Update unittests and their comments.
* Rename some functions for clarity.
Clean up Makefile.
Add new parameter lb.eqdist.eqDistForm.

Also create this new module and move relevant things from
dlbc.lb.collision.
Introduce dlbc.lb.tau parameter.
[Bugfix] Put tau in effect of force on velocity shift.
Add lb.eqdist.eqDistForm = EqDistForm.ThirdOrder.
Fix broken equation comment.